Models of radiofrequency coupling for negative ion sources

Area of Science:

• Plasma Physics
• Ion Source Technology
• Radiofrequency Heating

Background:

• Radiofrequency (RF) heating is crucial for inductively coupled plasma (ICP) ion sources.
• Heating efficiency is affected by operating pressure, Faraday shield, coil geometry, frequency, and magnetic fields.
• A magnetic filter is essential for H(-) ion survival in negative ion sources.

Purpose of the Study:

• To investigate factors influencing RF heating in ICP ion sources.
• To present an effective plasma conductivity model.
• To demonstrate the application of this model in plasma transport and heating simulations.

Main Methods:

• Single particle simulations were used to analyze electron acceleration.
• An effective plasma conductivity model was developed, incorporating static magnetic field effects.
• Multiphysics tools were employed for plasma transport and heating modeling.

Main Results:

• Electron acceleration was observed in the preglow regime for a 15 cm driver chamber radius.
• The effective plasma conductivity depends on electron density, temperature, RF field, and static magnetic field.
• The developed conductivity model was successfully applied to a small ICP source.

Conclusions:

• The study provides insights into optimizing RF heating in ICP ion sources.
• The new plasma conductivity model enhances the accuracy of plasma transport and heating simulations.
• The findings are relevant for the design and operation of ICP ion sources, particularly for negative ion generation.